1. Field
The presently disclosed subject matter relates to a light source and a vehicle lamp, and more particularly to a light source device using at least one LED chip and to a vehicle lamp such as a headlight, auxiliary headlight, or other vehicle lamp using the light source device.
2. Description of the Related Art
A conventional light source device using at least one LED chip for a vehicle lamp is disclosed in patent document No. 1 (Japanese Patent Application Laid Open JP2005-005193). FIG. 11 is a perspective view showing a conventional LED light source disclosed in patent document No. 1. FIG. 12 is a cross-section view of the conventional LED light source taken along line A-A shown in FIG. 11.
The conventional LED light source 90 includes: a blue LED chip 92 mounted in a metallic casing 91 and electrically connected to electrodes for receiving a power supply; a yellow phosphor 93 covering the LED chip 92; a transparent material 91a such as a glass and the like sealing both the LED chip 92 and the yellow phosphor 93 along with the metallic casing 91; and a shield material 94 located underneath the transparent material 91a. 
The yellow phosphor 93 can convert a blue light emitted from the blue LED chip 92 into a yellow light, and therefore the blue light of the blue LED chip 92 is converted into a white light via a yellow/blue color mixture. In this case, the shield material 94 can form such a shape as to shield a portion of the emitted light in order to conform to a light distribution standard for a vehicle lamp.
Thus, the conventional LED light source 90 can emit such a white light as to be able to conform to a light distribution standard for a vehicle lamp via the transparent material 91a by changing the shape of the shield material 94. More specifically, when designing a vehicle lamp using the LED light source 90, the vehicle lamp can be composed by locating an aspheric lens in front of the LED light source 90 which includes shield material 94 that is formed in a shape that conforms to a light distribution standard. The reason is that the light emitted from the LED light source 90 can be enlarged and projected ahead via the aspheric lens in accordance with the shape of the shield material 94.
However, when a headlight for a low beam is composed of the conventional LED light source 90, approximately half of the light emitted from the blue LED chip 92 can be shielded by the shield material 94 due to shielding an upward glare light. Thus, the light use efficiency of the light source 90 may be low, and also the power efficiency may be low because a power supply is used for both the unshielded light and for the shielded light. In addition, the low power efficiency may cause such a problem as generating a large amount of heat.
LED chips for the light source that may solve the above-described problem are disclosed in patent document No. 2 (Japanese Patent Application Laid Open JP2005-085549) and patent document No. 3 (Japanese Patent Application Laid Open JP2005-085895). FIG. 13 is a perspective view showing a conventional LED chip for a light source disclosed in patent documents No. 2 and 3.
The conventional LED chip 80 includes: a sapphire substrate 81; a n-type semiconductor layer 82 formed on the sapphire substrate 81; another n-type semiconductor layer 82a formed in a shape of a light distribution pattern and formed on the n-type semiconductor layer 82 and; a p-type semiconductor layer 83 formed on the other n-type semiconductor layer 82a, and a light-emitting layer 84 formed at a boundary surface between the other n-type semiconductor layer 82a and the p-type semiconductor layer 83; a p-type electrode 85 formed on the p-type semiconductor layer 83; and a n-type electrode 86 formed on the n-type semiconductor layer 82.
According to the structure of the LED chip, the LED chip 80 can emit light having a light distribution pattern emitted in according with the shape of the other n-type semiconductor layer 82a. Thus, because the LED chip 80 may not emit light that is subsequently shielded for a vehicle lamp, the light use efficiency thereof may be high.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: Japanese Patent Application Laid Open JP2005-005193    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2005-085549    3. Patent Document No. 3: Japanese Patent Application Laid Open JP2005-085895
In the above-described LED light source 90 shown in FIGS. 11 and 12, if the light-emitting area thereof can become large and the light intensity thereof can become high, the LED light source 90 may be more favorable to a vehicle lamp using it. The reason is that the vehicle lamp can illuminate a predetermined area with a high brightness while maintaining a low enlargement factor for the aspheric lens.
However, the light source 90 can be required to enlarge the size of the LED chip 92 therein and/or can be required to increase the number of the LED chip 92 in order to achieve the above-described characteristics, and therefore a driving current thereof might be increased. Thus, the power efficiency of the light source 90 may become lower, and the lower power efficiency thereof may cause a larger amount of heat. Moreover, because some of the emitted light is shielded by the shield material 94 may increase, the light use efficiency may also become lower.
In the above-described LED chip 80 shown in FIG. 13, because it may be possible to use all of the light emitted from the light-emitting layer 84 thereof, the power efficiency of the LED chip 80 may certainly improve with respect to the amount of light emitted from the vehicle lamp using it. However, it can be difficult to form such the light-emitting layer 84 as the above-described shape of light distribution pattern in the manufacturing process of the LED chip 80.
For instance, after a light-emitting layer can be formed by growing a p-type semiconductor layer over all or most the n-type semiconductor layer 82, the light-emitting layer 84 may be required to form a favorable shape using an etching, etc. Therefore, because the manufacturing process may become complex and may require a high processing accuracy, such problems as decreasing a yield, increasing the number of the manufacturing process and the like may result. In addition, the vehicle lamp using the LED chip 80 may include such a problem that a bonding wire shown in FIG. 13 can cause a shadow in the light distribution pattern thereof.
The disclosed subject matter has been devised to consider the above and other problems and characteristics. Thus, an embodiment of the disclosed subject matter can include LED light sources with high light use efficiency and a favorable brightness distribution and which can be made with a simple manufacturing process, and can include vehicle lamps with a favorable light distribution pattern and which also can be simply composed by using the LED light sources.